1. Field of the Invention
The present invention relates to an encoder.
2. Description of the Related Art
Japanese Patent Laid-Open No. (“JP”) 2007-248359 discloses an absolute encoder configured to output a monotonously increasing or decreasing signal as a scale moves. The absolute encoder including the scale having an optical pattern that combines a stripe pattern with a triangular pattern. Since a light receiving amount of a light receiving element continuously changes with the position of the scale, an analog signal is converted into absolute position information.
However, JP 2007-248359 causes detection errors because the light receiving amount of the light receiving element fluctuates due to the fluctuation of the emitted light amount of the light source and the uneven in-plane reflectance or transmittance. In addition, an apparatus is likely to become large because it requires a monitoring light receiving element and a reference pattern so as to correct a light amount.